Inspection apparatus and inspection method for pattern profile, and exposure apparatus

ABSTRACT

Disclosed is a pattern inspection apparatus which easily and highly accurately detects a profile error (deviation) of at least one pattern having a cross section with projections and recesses. The inspection apparatus for the pattern  32  is for detecting the profile error of the pattern having a cross section with a projection and a recess. This inspection apparatus includes a plate  30  on which a pattern is mounted, light sources  40, 42  and  44  which can change angles of illuminating light emitted onto the pattern, within a range of  15  to  75  degrees with reference to the top surface of the pattern, and photodetectors  52  and  54  which can receive reflected light from the pattern at an angle within a range of  15  to  75  degrees with reference to the top surface of the pattern. The inspection apparatus is characterized by that the profile error of the pattern is detected based on an amount of the reflected light from an edge between the top surface and the side surface of each of the patterns.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/497,053, filed Feb. 10, 2005.

TECHNICAL FIELD

The present invention generally relates to a pattern inspectionapparatus which detects a profile error (deviation) of a pattern havinga cross section with projections and recesses, and more particularly toan inspection apparatus and an inspection method which determinepresence and absence of defective deformation of a photoresist patternformed on a substrate such as a wafer.

BACKGROUND ART

In a manufacturing process of semiconductor devices, a photoresistpattern hereinafter, simply referred to as a resist pattern) is formedon a wafer as a mask for forming a circuit pattern. The resist patternis formed in a manner that a mask pattern is exposed onto a resistapplied on the wafer, using a stepper or a scanning exposure equipment,and then an exposed portion or an unexposed portion is removed(developed). When performing fine patterning of various patterns ofsemiconductor devices, it is particularly important to fabricate theresist pattern with good accuracy to conform to its design dimensions asmuch as possible.

The resist pattern may not be property formed as designed because of adefocus (out of focus) or the like during exposure. Specifically theresist pattern is formed, deviating from the design dimensions. When thewafer is mounted on a mounting stage, adsorbed to maintain a surface ofthe wafer flat and then exposed, this defocus occurs when the surface ofthe wafer is not flat due to a foreign matter such as dirt and dustbetween the back surface of the wafer and the surface of a stage, orwhen the height of the resist surface is uneven for various reasons suchas nonuniform application of the resist.

Conventionally, defective formation (profile error) of the resistpattern due to a defocus has been inspected utilizing diffracted lightwhich is generated when the resist pattern is illuminated with light asdiffraction grating. For example, in Japanese Patent Laid-OpenPublication No. 2001-141657, presence or absence of a defocused portionis detected by capturing a color difference which is considered adiffraction angle difference of diffracted light which is generated fromthe defocused portion and a normal portion of the resist pattern.

As miniaturization of semiconductor devices has advanced, a pitch of thepattern formed on the wafer has become too small to generate thediffracted light using visible light. For example, in order to generatediffracted light from a fine wafer with a pitch of about 0.1 micrometers(100 nm), light in an ultraviolet region with a shorter wavelength (400nm or shorter) than that of the visible light must be used as a lightsource, as described in, for example, Japanese Patent Laid-OpenPublication No. 2000-338049. However, when ultraviolet light is used,the resist pattern is exposed. Further, since ultraviolet light isinvisible to humans, setting of the optical system or measurement of thediffracted light requires enormous effort and time. Furthermore, anultraviolet sensor used as a photodetector is expensive, and it issometimes difficult to even procure an ultraviolet sensor for a largearea.

Moreover, to utilize the diffracted light means that the diffractionangle is varied depending on a difference of patterns on the wafer.Specifically, it is required to carry out a macro observation in whichthe defective formation of the resist pattern due to defocus is observedfrom every angle and direction, and this has been a great disadvantagein reducing inspection time and automating the macro inspection.

An object of the present invention is to easily and highly accuratelydetect a profile error (deviation) of a pattern having a cross sectionwith projections and recesses.

Another object of the present invention is to easily determine presenceor absence of a defocus of a resist pattern.

DISCLOSURE OF THE INVENTION

In the present invention, a profile error of a pattern is detected bymonitoring an amount of reflected light from an edge between top andside surfaces of the pattern having a cross section with projections andrecesses. Specifically, the present invention detects a profile error ofa pattern, considering that the profile error of the pattern includingthe edge is small when the amount of reflected light which is receivedby a photodetector from the edge of the pattern is large, and, on thecontrary, the profile error of the pattern including the edge is largewhen the amount of reflected light from an edge is small.

The present invention provides a new optical system for detecting aprofile error of a pattern by monitoring the amount of reflected lightfrom an edge between top and side surfaces of a pattern having a crosssection with projection and recess. In that case, the present inventionhas a characteristic to microscopically and highly accurately detect aprofile error of a fine pattern by a simple optical system using visiblelight for general use, without utilizing ultraviolet light anddiffracted light.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view comparing a edge shape of a resist pattern of adefocused portion and that of a normal resist pattern.

FIG. 2 is a view showing a difference in incident angles of illuminatinglight from the resist pattern of the defocused portion and the normalresist pattern.

FIGS. 3( a) and 3(b) are views of a resist pattern inspection apparatusand an inspection method according to the present invention; FIG. 3( a)is a schematic view of a resist pattern inspection, and FIG. 3( b) is anenlarged view of a main part of FIG. 3( a).

FIG. 4 is a view showing the surroundings of light including a diffusionangle γ of the illuminating light.

FIG. 5 is a view showing an equivalent model of the resist pattern.

FIG. 6 is a view showing positions of a light source and an eye wherethe illuminating light cannot be viewed.

FIG. 7 is a view showing an example of an automatic inspection apparatususing a CCD of the present invention.

FIG. 8 is a view showing rotation of a wafer on a stage.

FIG. 9 is a view showing a direction in which the illuminating light isemitted onto the resist pattern.

FIG. 10 is a view showing a control flow in an inspection PC of FIG. 7.

FIG. 11 is a view showing a measurement result of a wafer measured by asystem of the present invention of FIG. 7.

FIG. 12 is a view showing the illuminating light emitted onto a topsurface of the resist pattern and the illuminating light emitted ontothe edge.

FIG. 13 is a graph showing the ratio of the illuminating light emittedto the edge thereof.

FIG. 14 is a view showing a difference in reflected light from theresist pattern of the defocused portion and the normal resist pattern.

BEST MODES FOR CARRYING OUT THE INVENTION

In description below, although only a resist pattern is used, anapplication target of the present invention is not limited thereto, andthe present invention can be applied to all patterns, each having atleast a plurality of continuous projections and recesses (thickness).For example, the present invention may be applied to a fine conductorcircuit pattern on a semiconductor device, grating for a semiconductorlaser, a color filter and the like.

A detection principle of the present invention is described beforedetailing an embodiment of the present invention. A profile error of apattern appears conspicuously at an edge between the top and sidesurfaces of the pattern (hereinafter, simply referred to as an edge).With the profile error (deviation), the shape of the edge deviates fromthe original shape that the edge should have. For example, as shown inFIG. 1, the edge 18 b of the resist pattern 12 b is curved more sharplythan the edge 18 a of the normal resist pattern 12 a. Specifically, theedge 18 b is curved inwardly. This is because a fuzzy image (maskpattern) is transferred to the resist due to the defocus duringexposure.

Therefore, as shown in FIG. 2, the edge 18 a of the normal resistpattern 12 a and the edge 18 b of the defocused resist pattern 12 b arerespectively different in incident angles θ and

of illuminating light Li with reference to the edges, and thus theangles of reflected light Lr with reference to the illuminating light Liare different. Specifically, the reflection angle of the reflected lightfrom the edge, out of incident light to the pattern, changes inaccordance with an inclination degree (angle) of the edge. When theposition (for example, an angle with reference to the top surface of thepattern) of the photodetector to receive the reflected light is fixed ata certain position (angle), the amount of reflected light from the edgeentering into the photodetector changes in accordance with theinclination degree (angle) of the edge. Specifically, as the inclinationdegree (angle) of the edge becomes larger, in other words, as thedefocus becomes larger, the amount of reflected light from the edgeentering into the photodetector becomes smaller. As a result, theprofile error of the pattern can be sensed by detecting the amount ofreflected light from the edge.

By relatively comparing the amounts of reflected light from the edge foreach of the edges or for each certain areas, the presence or absence andthe distribution of the profile errors in the patterns arranged twodimensionally can be macroscopically obtained. In other words, even whenthe patterns are formed two dimensionally over a wide area, the profileerrors of the patterns can be obtained as a two dimensional distribution(macroscopic) by measuring the patterns while scanning each appropriatearea.

In the present invention, the detection principle thereof isfundamentally different from that of the conventional method using adiffracted light or coherent light. Specifically, in the presentinvention, the largest possible amount of reflected light from the edgeis detected by excluding (so as not to detect) diffracted light andcoherent light as much as possible. Accordingly, used in the presentinvention are a positioning of the optical system, a characteristic ofan optical element and the like which are different from those of theconventional method. In the present invention, in order to obtain themaximum detection sensitivity, used are, for example, a positioning ofthe optical system, characteristics of an optical element and the likeas described below, which are different from those of the conventionalmethod.

(a) A uniform surface emitting light source is preferred as a lightsource.

(b) The light source is preferably located at a position where the edgeportion of the resist is illuminated with light. Alternatively, thelight source is located so that the uniform surface emitting lightsource can be observed by the photodetector.

Further, it is preferable that light be incident to the edge between thetop and side surfaces of the pattern, from an almost perpendiculardirection with reference thereto.

(c) It is preferable that the light source be a luminous flux withdirectivity of a predetermined angle (for example, about 35 degrees) orsmaller.

(d) It is preferable that the light source have an oblong (stick-like)shape, for example, a size of 20 mm % 300 mm, for giving the luminousflux directivity.

(e) A CCD, for example, can be used as the photodetector, and a linesensor type CCD which is capable of detecting light with directivity ispreferred to an area sensor type CCD.

The pattern inspection apparatus and inspection method of an embodimentof the present invention is described in detail hereinbelow using thedrawings. In this specification, as an example, description is providedregarding a case of inspecting a resist pattern in which a silicon waferis used as a substrate and which is formed after exposing a positiveresist, which is applied onto the wafer, using a scanning exposureequipment, and thereafter removing unnecessary portions of the resist.Further, this resist pattern has a thickness of, for example, 0.6 to 0.7micrometers (μm). Note that detection can be performed even when theresist has an even smaller thickness of, for example, 0.1 micrometers(μm) or smaller.

FIGS. 3( a) and 3(b) are views showing how light is illuminated andreflected in the pattern inspection apparatus of the embodiment of thepresent invention. The pattern inspection apparatus includes the lightsource S for illuminating the resist pattern 12 formed on the wafer 14with the illuminating light Li, and a light receiving means P forreceiving the reflected light Lr which is the illuminating light Lireflected by the edge of the resist pattern 12. The whole or a part ofresist pattern 12 is illuminated with the illuminating light Li. Thereceiving means receives the reflected light Lr reflected by the edgeand a smallest possible amount of reflected light from the top surface.The detection sensitivity is improved by receiving as much the reflectedlight Lr reflected by the edge as possible.

In FIG. 3, the stage 16, where the wafer 14 is placed, is circular andis freely rotatable in a circumferential direction about an axis, whichis a line perpendicularly passing through the center point of thecircle.

It is preferable that the illuminating light Li be monochromatic lightfor better sensitivity and visibility when the light receiving meansreceives the reflected light Lr. However, the illuminating light Li isnot limited thereto for detection. The illuminating light Li may belight including a certain wavelength or a plurality of wavelengthssimilar thereto. For the light source S, a surface emitting light sourceis used, which is constructed as an array having a plurality of lightemitting diodes (LEDs) arranged vertically and horizontally, such thatthe illuminating light Li illuminates the entire resist pattern 12.

In order to receive the reflected light Lr which is reflected by theedge, the wavelength of the illuminating light Li is preferably within arange of about 400 to 700 nanometers (nm) in a visible light region. Ina case of using visible light, the amount of reflected light can berecognized by brightness (lightness) of the reflected light Lr. Notethat, however, the illuminating light Li is not limited to visiblelight, and may be light with a different wavelength region such as aninfrared light, as long as it does not include a wavelength whichexposes the resist (ultraviolet light).

FIG. 4 is a view showing the surroundings of the light source of anembodiment of the present invention. In FIG. 4, a diffusion plate 13 isplaced in front of the LEDs, and a diffusion angle γ (an angle of anuppermost or lowermost light beam with reference to a center light beam)of the illuminating light Li from the light source S is set to be 35degrees or smaller. The reason why the diffusion angle γ is set to be 35degrees or smaller is because it was learned, as a result of varioustests, that this angle is optimal to improve the detection sensitivitywhile eliminating unnecessary light such as reflected light from areasother than the edge, diffracted light, scattered light and the like.Examples in constructions of the LED and the diffusion plate are shownbelow. Note that, however, the LED may be one having a differentwavelength.

<Examples in Constructions of LED and Diffusion Plate>

-   -   LED: Dominant wavelength: 535 nm, Light intensity: 3.4 cd,        Directional pattern: ±15 degrees, Number: 240,        -   Size: 250 mm % 48 mm    -   Diffusion plate: Transmittance: 60%

The surface emitting light source using the LEDs is preferred foruniformizing luminance of a light emitting surface to obtain a higherdirectivity of the illuminating light. The surface emitting light sourceis capable of illuminating a wide area with the illuminating light Li atonce. Therefore, when the reflected light Lr is received by the lightreceiving means, a difference in the reflection light from the normalportion and the defocused portion can be clearly identified. Further,since the surface emitting light source can illuminate a wide area withthe illuminating light Li, measurement can be carried out without movingthe light source S or the substrate 14 when an inspection is conducted.

Light from the light source S is required to be emitted to the topsurface of the resist pattern 12, slanting at an angle within a range of15 to 75 degrees, more preferably 30 to 50 degrees, with reference tothe top surface of the resist pattern 12. Further, it is preferable thatreflected light be received by the receiving means, slanting at an anglewithin a range of 15 to 75 degrees with reference to the top surface ofthe resist pattern 12. The reasons for the above are as follows.

From the results of the tests, it was found out that the reflected lightfrom the resist edge generated by light illumination can bemacroscopically calculated by approximating the shape of the resistusing an equivalent model shown in FIG. 5. Specifically, an approximatereflection angle with reference to a light illumination (incident) anglemay be obtained by the following equation:

θ=180−θin−2θo  (1)

wherein θ denotes the reflection angle, θin denotes the lightillumination angle and θo denotes the resist edge angle.

Further, from the cross sectional shapes of the resist patterns with aplurality of line widths observed by SEM or the like, it was found outthat all shapes of the resist patterns are represented by an inclinationangle θo of the edge portion within a range of 30 to 70 degrees. Inaddition, a relationship between the reflection angle and theinclination angle of the resist edge within a range from the maximumillumination angle of 75 degrees to the minimum illumination angle of 15degrees was obtained using equation (1). Consequently it was found outthat all the reflected light from the resist edges having inclinationangles within a range of 30 to 70 degrees has reflection angles between15 and 75 degrees with respect to the light illumination angles between15 and 75 degrees. Specifically, it was found out that the light sourceshould cover the light illumination angles between 15 and 75 angles andthe photodetector is to cover the light receiving angles between 15 and75 degrees, when attempting to receive the reflected light from theresist edge portions of all shapes. In other words, the illuminatinglight Li is reflected to the opposite side of the photodetector P (FIG.3) when the light illumination angle is 15 degrees or smaller, whereasthe illuminating light Li is reflected in a direction towards thesubstrate 14 when the light illumination angle is 75 degrees or larger.Therefore, the reflected light Lr cannot be received by thephotodetector P.

The photodetector includes, for example, a camera P using a CCD (chargecoupled device) as a light receiving element. The reflected light Lrreceived by the CCD is converted into image data as detailed later.Image processing of the image data is her performed to detect thedefocused portion. For example, with image processing, a portion wherethe image data suddenly changes due to the amount of the reflected lightfrom the edge is detected as a difference in brightness (lightness),thus the normal portion and the defocused portion is distinguished. Whenthe camera P is used, it is feasible to automate the inspectionapparatus 10 as described later. Further, the human eye may be usedinstead of the camera P. In this case, the reflected light Lr is viewedto distinguish the normal portion and the defocused portion by thedifference in the reflected light Lr.

As mentioned earlier, the camera P is generally located at a positionabove the top surface of the resist pattern 12 within a range of 15 to75 degrees with reference thereto. Further, when the reflected light Lrcan be received even at the angle within a range of 15 to 75 degrees,the camera P may be located at a position within the range. However, asshown in FIG. 6, the camera P cannot identify the reflected light Lr ifthe light source S and the camera P are located on the same line withthe illuminating light Li. Hence, the angle positions of the lightsource S and the camera P are required to be moved away from each other,but the light source S and the camera P are required to be located onthe same side with reference to the resist pattern 12. When the lightsource S is located at a position at an angle within a range of 15 to 75degrees with reference to the top surface of the resist pattern 12, anangle β formed by the illuminating light Li and the reflected light Lris changeable within an angle range of about plus or minus 60 degreeswith reference to the illuminating light Li.

It is preferable that a distance between the light source S and theresist pattern 12 be, for example, within a range of 300 to 600 mm. Thisis because, if the distance between the light source S and the resistpattern 12 is too long, illumination intensity on the resist pattern 12is reduced and a contrast of the reflected light Lr is deteriorated.Thus, the defocus is overlooked. On the contrary, if the distancebetween the light source S and the resist pattern 12 is too short, thecontrast of the reflected light Lr is deteriorated, and the illuminationintensity on the resist pattern 12 becomes too high. Consequently, inthe case of viewing the resist pattern 12 with a human eye, the eye getstired easily and an illuminated area on the resist pattern 12 with theilluminating light Li becomes small.

It is also preferable that the distance between the resist pattern 12and the camera (or the eye) P be, for example, within the range of 300to 600 mm. This is because, if the camera P is too close to the resistpattern 12, a field of view becomes narrow, and, if the camera P is toofar from the resist pattern 12, the contrast of the reflected light Lris deteriorated.

The positions of the light source S and the camera (or the eye) P may befixed within the above mentioned range. This is because, the angle ofthe reflected light Lr with reference to the illuminating light Li isconstant. Therefore, the present invention can be utilized for anautomatic inspection apparatus using the CCD whose demand is expected inthe future.

FIG. 7 is a view showing an automatic inspection apparatus using the CCDof the embodiment of the present invention. In FIG. 7, the substrate(wafer) 32 having patterns to be measured is mounted on the circularstage (work) 30. The stage 30 is rotated or moved horizontally orvertically by a linear motor 34 controlled by a controller 36. As shownin FIG. 8, the stage 30 is rotated by 90 degrees in a circumferentialdirection so that the inspection can be carried out from a differentdirection. This is because, when the resist pattern 12 is orientated inX and Y directions and light is emitted from point A as shown in FIG. 9,the inspection of the resist pattern 12 orientated in the Y directioncan be carried out by the aforementioned method, whereas the inspectionof the resist pattern 12 orientated in the X direction needs to becarried out from a plurality of directions since the emitted light isnot reflected toward the direction of point A.

Used as the light source are lights 40, 42 and 44 for three light beamsA, B and C, respectively, with different illumination angles. Thepositions of the respective lights can be changed along a predeterminedare by a motor 46 which is controlled by a controller 48. The angles ofthe respective lights can be changed within a range of 15 to 75 degreeswith reference to the top surface of the pattern on the work. Note thatthe number of lights is set to three for a further improvement of thedetection sensitivity, but the detection can be feasible with at leastone light or more. At least one of the lights is positioned to beperpendicular to the edge of the resist pattern on the wafer. In FIG. 7,the light A (40) is located at a position within a range of 48 to 52degrees, the light C (44) is located at a position within a range of 16to 18 degrees, and the light B (42) is located to be approximatelycoaxial with a CCD line sensor. The brightness of the light beams isadjusted by a power source 50 for lighting.

Similar to the lights, the position of a CCD line sensor camera 52 canbe changed along the predetermined are by the motor 46 which iscontrolled by the controller 48. The light receiving angle of the camera52 can be changed within a range of 15 to 75 degrees with reference tothe top surface of the pattern on the work. A camera 54 for monitoringis attached to the camera 52. The outputs from the controllers 36 and 48of the motor, the power source 50 for lighting and the cameras 50 and 52are connected to an inspection personal computer (PC) 56. The inspectionPC 56 controls each of the controllers and the power source forlighting, based on a predetermined automatic measuring program. By aninstruction from the inspection PC 56, an image pickup optical system(positional relationship between the lights and line sensor camera) isarbitrarily set in accordance with an inspection target.

The image pickup optical system (positional relationship between thelights and the line sensor camera) and the angles shown in FIG. 7 areset as follows. Specifically, they are set so as to exclude unnecessaryscattered light and diffracted light and to detect subtle shape changesof the resist with good sensitivity. Here, the most important point indesigning the system is that the diffracted light from the inspectedwafer does not return to an angle at which the line sensor camera 52 isplaced, and only the reflected light from the resist edge portion istaken out with a good contrast. Accordingly, the diffracted lightgenerated from the pattern on the wafer used as diffraction grating wascalculated using a reflection grating model, and a positionalrelationship was set so that the diffracted light did not return to theangle at which the CCD line sensor exists when a dedicated reticle wasused. It should be noted that an optimal pickup angle may be changeddepending on the resist shape in setting the positional relationship.

FIG. 10 shows a control flow (automatic measurement flow) by the use ofthe inspection PC 56 of FIG. 7. Three lights are turned on (step 60).The camera 52 receives the reflected light from the pattern on the wafer32 (step 62). A capture card within the PC 56 receives the output fromthe camera 52 and the value (digital value) of the output is stored in amemory as image data (step 64). The size of the digital valuecorresponds to the amount of the reflected light. The angle of thecamera is changed by controlling motor 46 (step 66). Steps 62 to 66 arerepeated and the image data (digital value) captured at each angle isstored in the memory. Based on the digital values obtained, the PC 56decides an angle of the camera 52 at which the detection sensitivity(density (intensity) of the image) is maximum (step 68). The camera 52is fixed at the decided angle.

Measurement positions on the wafer are set by controlling the motor 34(step 70). After the wafer is moved to the first measurement position,measurement is carried out similar to the steps 62 and 64, and imagedata is stored in the memory (step 72). The steps 70 and 72 arerepeated, and the measurement is sequentially carried out while scanningthe measurement positions on the wafer. At this time, since the camera52 is a line sensor camera, the measurement is carried out while movingthe wafer by each line at predetermined intervals. The measurement isconducted until all measurement points (lines) are completely measured.Using measurement data, the PC performs mapping of the image data ateach position on the wafer as a two dimensional image (step 76). Thepresence or absence of the profile error (defocused portion) of thepattern on the wafer can be detected from the intensity (color density)in the mapped image information.

FIG. 11 shows a measurement result of the wafer which was actuallymeasured by the use of the system of the embodiment of the presentinvention in FIG. 7. FIG. 11 is a measured resist pattern with a linewidth of 0.3 micrometers. Approximate quadrangle and dark (dense)portions of the image in FIG. 11 show where the profile errors (rolloffs at the edge of the patterns) exist. The profile errors weregenerated due to de-synchronization (errors) while scanning wasperformed by the stepper which exposed the resist pattern. Since thestepper used synchronizes by each reticle having 3% 4 chips, i.e. 12chips, the profile errors are generated per area of one reticle. Theseprofile errors are inevitably generated due to synchronization accuracyof the stepper while scanning. In the tests conducted by the inventors,almost none of the profile errors that are inevitably generated could bemeasured with the conventional method utilizing diffraction. However,with the apparatus of the embodiment of the present invention in FIG. 7,the profile errors can be detected as a clear image as shown in FIG. 11.

With the inspection apparatus of FIG. 7, exposure conditions for thephotoresist can be adjusted based on the detected profile errors of thepatterns. Therefore, the inspection apparatus can be incorporated intoan exposure apparatus or stepper as a part of them. Specifically, thereis an advantage that the exposure conditions (defocus) can be adjustedwithin a production line of semiconductor devices by providing theexposure apparatus or the stepper with means (flow) for adjusting theexposure conditions for the photoresist based on the profile errors ofthe patterns, which were detected by the inspection apparatus of FIG. 7.Further, it is possible to detect characteristics such asde-synchronization (error) between the wafer and the reticle possessedby the exposure apparatus or the stepper while being scanned, anautofocus tracking performance, an error of a leveling mechanism anddistortion of a lens. Finally, description is given again regarding acase where the inspection apparatus of the present invention can beeffectively used. As described earlier and shown in FIG. 3, in theinspection apparatus of the present invention, the profile error(defective formation) of the resist pattern 12 due to defocus isinspected by illuminating the edge of the resist pattern 12 with theilluminating light Li and receiving the reflected light Lr by the use ofthe CCD of the camera P. Therefore, the larger the ratio of the edgearea of the resist pattern 12 is, the more the reflected light Lr can bereceived by the CCD of the camera P. Thus, the inspection apparatus 10can be effectively used.

As shown in FIG. 12, when a width of the illuminating light Li emittedto the top surface 20 of the resist pattern 12 is denoted by a and awidth of the illuminating light Li emitted to the edge 18 is denoted byb, the ratio A of the illuminating light Li emitted to the edge 18 isexpressed by the following equation.

A=b/(a+b)%100

FIG. 13 shows a graph of a relationship between the pitch of the resistpattern 12 (the sum of a pattern width and a pattern interval) and theratio of the illuminating light Li emitted to the edge 18. As shown inFIG. 13, the ratio of the forgoing illuminating light Li is suddenlyincreased when the pitch is between 0.8 μm (pattern width/patterninterval=0.40 μm/0.40 μm) and 0.6 μm (pattern width/patterninterval=0.29 μm/0.31 μm). The inspection apparatus 10 of the presentinvention can be effectively used for the inspection of the resistpattern 12 having a pitch finer than 0.6 μm. However, according to thetest conducted by the inventors, since the reflected light Lr can beconfirmed, when the inspection is for the resist pattern 12 with a ratioof 50% or more of the illuminating light Li emitted to the edge 18, theinspection apparatus 10 can be used. This is because the ratio of theedge 18 in the entire resist pattern 12 is increased as the resistpattern 12 becomes finer, and the edge 18 is in a mirror-like state whenthe resist pattern 12 is viewed from the light source S. Therefore, ifthere is defective formation of the resist pattern 12 due to defocus,only the defectively formed portions (the resist patterns 12 b shown bydiagonally shaded portions in the drawing) have different angles of thereflected light Lr, and thereby the normal portion and the defocusedportion can be distinguished. This is because there is difference in theamount of light received by the photodetector positioned at apredetermined angle.

The embodiment of the present invention has been described. However, thepresent invention is not limited to the above mentioned embodiment. Forexample, by enabling the positions of the light source S and the cameraP to be changed within the aforementioned range, the reflected light Lrfrom the edge 18 of the resist pattern 12 can be received, and, inaddition, diffracted light may be received by using the resist pattern12 as diffraction grating depending on the positions of the light sourceS and the camera P. In this case, in order to receive the diffractedlight, the mounting stage 16 is constructed to be able to slant at anarbitrary angle using a line passing though the center of the mountingstage 16 as an axis. By constructing as above, the inspection apparatus,unlike the foregoing inspection apparatus and the conventionalinspection apparatus, can surely carry out the inspection even in thecase where there is a plurality of pattern widths of the resist pattern12.

Moreover, the defocused portion can be surely inspected by appropriatelyusing the inspection apparatus 10 of the present invention and theconventional inspection apparatus utilizing diffracted light, dependingon the ratio of the illuminating light Li emitted to the edge 18. Whenthere is the plurality of pattern widths of the resist pattern 12, theinspection is surely carried out by using the inspection apparatus ofthe present invention and the conventional inspection apparatus.

Although LEDs are used for the light source S, the light source S mayhave a construction including a halogen lamp and filters instead ofLEDs. Light including a wavelength between first and second wavelengthsis taken out from the light of the halogen lamp by a filter which cutsoff light with the first wavelength (short wavelength) or shorter andthe filter which cuts off light with the second wavelength (longwavelength) or longer. The first and second wavelengths are those whichconform to conditions of the aforementioned LEDs. A filter which passesonly light including the wavelengths between the first and secondwavelengths can be used instead of the two filters.

Apart from the above, the present invention can be carried out in a modeto which various improvements, alterations and modifications are addedbased on the knowledge of those skilled in the art, in the scope notdeparting from the gist of the present invention.’

According to the present invention, a profile error (deviation) of apattern having a cross section with projections and recesses can bedetected easily with high accuracy. According to the present invention:presence or absence of a defocus which occurs during exposure of aresist pattern can be easily detected. According to the presentinvention, it is possible to easily detect the presence or absence of aprofile error (deviation) of a fine resist pattern having a patternwidth of about 0.1 micrometer or smaller, which could not be detectedwith a conventional method utilizing diffracted light.

1. A pattern profile inspection apparatus for detecting a profile errorof at least one pattern having a cross section with a projection and arecess, the inspection apparatus comprising: a plate on which thepattern is mounted; a light source which can change an angle ofilluminating light to the pattern within a range of 15 to 75 degreeswith reference to a top surface of the pattern; and a photodetectorwhich can receive reflected light from the pattern at an angle within arange of 15 to 75 degrees with reference to the top surface of thepattern, wherein the profile error of the pattern is detected based onan amount of the reflected light which is received by the photodetector,from an edge between the top surface and a side surface of each of thepatterns, wherein when the edge has a surface area of the pattern havingthe profile error, the amount of the reflected light received by thephotodetector is greater than an amount of reflected light for the edgeof the pattern not having the profile error.
 2. A pattern profileinspection apparatus for detecting a profile error of a pattern having across section with a projection and a recess, the inspection apparatuscomprising: a plate on which the pattern is mounted; a light sourcewhich can change an angle of illuminating light to the pattern within arange of 15 to 75 degrees with reference to a top surface of thepattern; and a photodetector which can receive reflected light from thepattern at an angle within a range of 15 to 75 degrees with reference tothe top surface of the pattern, wherein an illumination angle from thelight source is decided to be almost perpendicular to an edge betweenthe top surface and a side surface of the pattern, wherein when the edgehas a surface area of the pattern having the profile error, the amountof the reflected light received by the photodetector is greater than anamount of reflected light for the edge of the pattern not having theprofile error.
 3. The pattern profile inspection apparatus according toclaim 2, further comprising at least one or more light sources havingillumination angles different from said illumination angle.
 4. Thepattern profile inspection apparatus according to claim 2, wherein thelight source includes a uniform surface emitting light source.
 5. Thepattern profile inspection apparatus according to claim 2, wherein thelight source has an oblong shape such that the illuminating light hasdirectivity.
 6. The pattern profile inspection apparatus according toclaim 2, wherein a light receiving angle of the photodetector is decidedsuch that a ratio of the reflected light from the edge of the patternout of said reflected light is maximum.
 7. The pattern profileinspection apparatus according to claim 2, wherein the light receivingangle a (degree) of the photodetector is decided to meet a relationshipexpressed by an equation of a=180−b−2c, where b denotes the illuminationangle (degree) with reference to the top surface of the pattern and cdenotes an inclination angle (degree) of the edge with reference to aplane that is parallel to the top surface of the pattern.
 8. The patternprofile inspection apparatus according to claim 2, wherein thephotodetector includes a line sensor.
 9. The pattern profile inspectionapparatus according to claim 2, wherein the photodetector includes a CCDcamera.
 10. The pattern profile inspection apparatus according to claim2, wherein the pattern includes a photoresist pattern provided on asubstrate.
 11. The pattern profile inspection apparatus according toclaim 2, further comprising: image processing means which receives anoutput signal of the photodetector and produces image informationcorresponding to an amount of the reflected light which is received bythe photodetector; drive means which changes positions of the lightsource and the photodetector in order to change the angle of theilluminating light and the light receiving angle of the reflected light;and moving means which makes the plate move in order to change aposition of the pattern illuminated with the illuminating light.
 12. Apattern profile inspection apparatus for detecting defective formationof a thick pattern formed on a substrate, the inspection apparatuscomprising: a plate on which the pattern is mounted; a light sourcewhich can change an angle of illuminating light to the pattern within arange of 15 to 75 degrees with reference to a top surface of thepattern; and a photodetector which can receive reflected light from thepattern at an angle within a range of 15 to 75 degrees with reference tothe top surface of the pattern, wherein an illumination angle from thelight source is decided such that a ratio of illuminating light emittedto an edge between the top surface and a side surface of the pattern outof the illuminating light is 50% or more, wherein when the edge has asurface area of the pattern having the profile error, the amount of thereflected light received by the photodetector is greater than an amountof reflected light for the edge of the pattern not having the profileerror.
 13. An exposure apparatus which exposes a photoresist provided ona substrate, comprising a pattern profile inspection apparatus fordetecting a profile error of at least one pattern of the photoresisthaving a cross section with a projection and a recess, the inspectionapparatus including: a plate on which the pattern is mounted; a lightsource which can change an angle of illuminating light to the patternwithin a range of 15 to 75 degrees with reference to a top surface ofthe pattern; and a photodetector which can receive reflected light fromthe pattern at an angle within a range of 15 to 75 degrees withreference to the top surface of the pattern, wherein a profile error ofthe pattern is detected based on an amount of the reflected light whichis received by the photodetector and from an edge between the topsurface and a side surface of the each of the patterns, wherein when theedge has a surface area of the pattern having the profile error, theamount of the reflected light received by the photodetector is greaterthan an amount of reflected light for the edge of the pattern not havingthe profile error.
 14. A pattern profile inspection method which detectsa profile error of at least one pattern having a cross section with aprojection and a recess, the method comprising the steps of: (a)illuminating a top surface of the pattern with light slanting withreference thereto; (b) receiving reflected light which is reflected byan edge between the top surface and a side surface of the pattern; (c)detecting the profile error of the pattern based on an amount of thereceived reflected light which is reflected by the edge; and (d) mappingthe profile error in the entire pattern as image information based onthe detected profile error of each of the patterns.
 15. The patternprofile inspection method according to claim 14, wherein the step of (a)illuminating the top surface of the pattern includes a step of emittinglight to the edge almost perpendicularly.